I noticed on the 04 & 05 Z's they list ABS, Electronic Brake force Distribution,
and Brake Assist as standard features. I've never seen brake assist listed on the standard feature list for the 03's, but they do list ABS and Electronic Brake force Distribution. Is brake assist a newer feature NOT available on the 03's ?

 

Maybe its the VDC? Same function...

 

The way I understand it, Brake Assist mesure the time it takes you to go from gaz to brake to detect an emergency braking situation. When it does, it will brake as hard as possible for you.

I haven't tried left foot braking yet, but if the system is the same as on some Audi, the car will brake like crazy when I do.

 

the Brake Assist distribute difference brake forces among the 4 wheels...
and I believe it was standard on 03s, at least in the VDC equipped models

 

What you describe is the EBD (Electronic Brake Distribution).

I've just checked in the Nissan Product Guide and confirm that the BA ito apply maximum braking power in the event of a rapide switch from thotle to brakes.